finding the error deviation - 4rth grade tf

sys5

sys5 =

18 s^2 + 20 s + 10

---------------------

s^4 + 2 s^3 + s^2 + s

Continuous-time transfer function.

>> ltiview(sys5)

////// I want to find how much is the error for my 4th grade tf with the help of ltiview at step response. My tf(sys5) has an (PID controller series with a tf) with a feedback(tf=1)